1. Field of the Invention
The present invention relates to a dielectric filter, a transmission-reception sharing unit, and a communication device for use in the microwave band and the millimeter-wave band.
2. Description of the Related Art
In order to achieve next-generation mobile and multimedia communications, ultra-fast transmission of a large amount of data is necessary. The millimeter-wave band having a large bandwidth can satisfy this requirement. In addition, in a field other than communications, shock-absorbing vehicle radar as a new form to take advantage of characteristics of the millimeter-wave band has been introduced. It is greatly anticipated that the millimeter-wave radar can ensure safety in fog or snow. Conventional laser radar using light lacks this capability.
When a conventional circuit structure composed almost exclusively of microstrip lines is used in a millimeter-wave band, loss increases due to reduction of Q. Furthermore, in a conventional type of widely used TE01xcex4 dielectric resonator, a large amount of resonant energy leaks out of the resonator. As a result, in the millimeter-wave band in which relative dimensions of a resonator and a circuit are small, undesirable coupling with the lines occurs, thereby creating difficulties in design and characteristic reproduction.
In order to solve these problems, a millimeter-wave band module using PDIC(trademark) (Planer Dielectric Integrated Circuit) technology is mentioned. An example of such a high-module dielectric resonator is shown in Japanese Unexamined Patent Application Publication No. 8-265015.
In the dielectric resonator mentioned above, an electrode is formed on each of the main surfaces of a dielectric plate; parts of the electrode are electrodeless so that the electrodeless parts on the dielectric plate may function as a dielectric resonator.
FIGS. 10A, 10B, and 10C respectively show an example in which a plurality of dielectric resonators is formed on a dielectric plate to constitute a dielectric filter. FIG. 10A shows a state in which the upper conductor plate of the dielectric filter is removed; FIG. 10B is a sectional view taken along the line Axe2x80x94A in FIG. 10A; and FIG. 10C is a sectional view taken along the line Bxe2x80x94B in FIG. 10A. In this figure, reference numeral 3 denotes a dielectric plate, on a first main surface of which an electrode 1 is formed having electrodeless parts 4a and 4b; and on a second main surface of the plate, an electrode 2 is formed having electrodeless parts 5a and 5b opposing the electrodeless parts 4a and 4b. Parts of the dielectric plate positioned between these electrodeless parts operate as TE010-mode dielectric resonators. Coaxial connectors 10 and 11 are formed in a cavity 8, and probes 6 and 7 are protruded from the respective central conductors thereof so as to respectively couple with the dielectric resonator. Magnetic-field coupling between the two resonators are allowed.
In the dielectric filter shown in FIGS. 10A, 10B, and 10C, spurious responses result in problems, as described below.
FIG. 11 shows attenuation characteristics of the dielectric filter shown in FIGS. 10A, 10B, and 10c. In this figure, responses of each mode are shown: reference characters (a) to (e) indicate HE110 mode, HE210 mode, HE310 mode, TE110 mode and TE010 mode respectively. As shown here, in addition to responses of the TE010 mode being the main mode, a number of unnecessary spurious responses occur. When these spurious responses coincide with frequencies in which specified attenuation levels are necessary, they may not satisfy requirements of the attenuation levels.
FIGS. 12A to 12E shows examples of magnetic field distributions of the above-indicated respective resonant modes. In these figures, solid lines indicate electric line of force, and broken lines indicate magnetic line of force. These lines show the magnetic field distributions. In each of the figures, the upper part shows a plan view of the dielectric resonator, and the lower part shows a view from the sectional direction of the dielectric plate.
FIGS. 13A to 13E show manners in which each mode may be coupling between the two adjacent dielectric resonators. As shown here, in any of the modes, magnetic-field coupling occurs between the adjacent dielectric resonators at their near parts.
The present invention provides a dielectric filter, a transmission-reception shared unit, and a transceiver, which incorporate the filter, in which spurious modes are suppressed to improve blocking-band attenuation characteristics.
The present invention also provides a dielectric filter including a dielectric plate; a first electrode formed on a first main surface of the dielectric plate, parts of the electrode being electrodeless; a second electrode formed on a second main surface of the dielectric plate, parts of the electrode opposed to the electrodeless parts of a first main surface being electrodeless; wherein the electrodeless parts on the dielectric plate form dielectric resonators; wherein the dielectric resonators are aligned linearly; and wherein an angle formed by the line and at least one of linearly-formed coupling members coupled with a specified one of the dielectric resonators is of a specified number of degrees other than 90 degrees.
Even in a spurious mode which couples between the aligned dielectric resonators, when the spurious mode is a mode which almost never couple with the linearly-formed coupling member forming a specified angle with the line along which the dielectric resonators are aligned, a response of the spurious mode is suppressed. For example, when the linearly-formed coupling member is disposed parallel to the line along which the dielectric resonators are aligned, responses of spurious modes such as HE110 mode, etc., are suppressed. In contrast, like the TE010 mode, when a mode capable of coupling, regardless of the angle formed by the coupling member and the dielectric resonator, is set as a main mode, there is no problem in terms of coupling in the main mode between the dielectric resonator and the coupling member, and also, coupling in the main mode between the adjacent dielectric resonators.
The other linearly-formed one of the coupling members coupled with a specified one of the dielectric resonators may be disposed perpendicular to the line along which the dielectric resonators are aligned.
In addition, since coupling with a specified spurious mode can be avoided according to the angle, the appropriate selection of the angle permits selective suppression of spurious modes.
Further, the present invention provides a dielectric filter including a dielectric plate; a first electrode formed on a first main surface of the dielectric plate, parts of the electrode being electrodeless; and a second electrode formed on a second main surface of the dielectric plate, parts of the electrode opposed to the electrodeless parts of a first main surface being electrodeless; wherein the electrodeless parts on the dielectric plate form dielectric resonators; and wherein the dielectric resonators are disposed in such a manner that the lines connecting the centers of respective adjacent dielectric resonators do not mutually coincide on the same line.
Even in the coupling of spurious modes between two adjacent dielectric resonators, the further-adjacent dielectric resonator is positioned at an angle, which differs from the transmitting direction of the spurious mode. Thus, this arrangement permits coupling with a specified spurious mode to be avoided according to the angle, and also permits selective suppression of spurious modes.